Between 2011 and 2012, the Center for Social Innovation, LLC (C4), developed and evaluated a prototype of the Motivational Interviewing Simulator: An Experiential Online Training Tool. The interactive, case-based, multiplayer web-based game allows service providers to deepen their skills in Motivational Interviewing (MI), a widely recognized evidence-based practice that supports people to make positive behavior changes related to health, wellness, mental illness, and addiction. Phase I study findings support the product's feasibility and the need for a large-scale randomized trial to determine the tool's effectiveness. During Phase I, participants in the Simulator group showed significant improvements in MI skills as measured by Motivational Interviewing Treatment Integrity (MITI) scores (34 percent improvement over baseline) and Helpful Responses Questionnaire (HRQ) scores (13 percent improvement over baseline)-both substantially higher than the rates of improvement for participants in the control groups. This project represents Phase II of the work to further develop the MI Simulator and to study its impact on provider behavior and client outcomes. Phase II will create multiple play arenas-Single Player, Two Player, and Advanced Freeplay spaces-and multiple case-based scenarios related to mental health, homelessness, addiction, and primary care. The significantly expanded product will have wide appeal across a large workforce of providers serving vulnerable populations, and it will support NIMH's strategy of closing the gap between the development of new, research-tested interventions and their widespread use by those most in need. The Phase II randomized controlled trial is guided by four specific aims: 1. Diversify the prototype Motivational Interviewing Simulator to meet the needs of a wider audience. 2. Evaluate the Simulator through a randomized controlled trial. 3. Disseminate Findings. 4. Prepare for Commercialization. During Phase II of this study, we will recruit 180 providers from 18 community agencies serving individuals who live in supportive housing, many of whom have histories of mental illness, addiction, homelessness, and medical problems. After receiving a standardized two-day onsite MI training, participants will be randomized into one of three conditions: 1) MI Training Only; 2) MI Training + eBook (an online comparison with comparable information to the Simulator without the interactive elements); or 3) MI Training + Simulator. The longitudinal, mixed method study will assess providers' acquisition and retention of MI knowledge and skills through surveys and coding of standardized client interviews; barriers and facilitators of MI implementation via focus groups; organizational-level data via key informant interviews and site visits; and client outcomes for 3,600 clients through surveys, administrative, data and focus groups.